# handle_info, handles
# GenServer.call(pid, {:something, :key})

Notice that you didn’t use match-all clauses for handle_cast and handle_call in previous examples.
This was intentional. Casts and calls are well-defined requests.
They specify an interface between clients and the server process. Thus an invalid cast means your clients are using an unsupported interface. In such cases, you usually want to fail fast and signal an error.


defmodule KeyValueStore do
  use GenServer

  def init(_) do
    {:ok , %{}}
  end

  def start do
    GenServer.start(KeyValueStore, nil)
  end

  def put(pid, key, value) do
    GenServer.cast(pid, {:put, key, value})
  end

  def get(pid, key) do
    GenServer.call(pid, {:get, key})
  end

  def handle_cast({:put, key, value}, state) do
    { :noreply, Map.put(state, key, value) }
  end

  def handle_call({:get, key}, state) do
    { :reply, Map.get(state, key) }
  end

  def handle_info(_, state) do
    {:noreply, state}
  end
end